1. Field of the Invention
Embodiments of the present disclosure relate to an image forming apparatus configured to form a color image through a multi pass scheme, and the control method thereof.
2. Description of the Related Art
In general, an image forming apparatus using an electro-photographic method is an apparatus configured to form an electrostatic latent image on a photosensitive medium by an exposure unit such as a laser scanning unit (LSU) by receiving a digital image signal that corresponds to a desired image, to form a toner image by supplying a toner to the electrostatic latent image by a developing unit, to transfer the toner image to an intermediate transfer belt and to form a desired color image by transferring the toner image to a recording medium.
The colors that are mostly used to form a color image are yellow ‘Y’ (Yellow ‘Y’), magenta ‘M’ (Magenta ‘M’), cyan ‘C’ (Cyan ‘C’), and black ‘K’ (black ‘K’). With respect to forming a color image through an electrophotographic method, a single pass scheme having the total of four exposure units and the total of four photosensitive media that correspond to each color, and a multi pass scheme having a single exposure unit and a single photosensitive medium are included.
The image forming apparatus of a multi pass scheme, when compared to the image forming apparatus of a single pass scheme, is provided with simpler mechanical composition, and thus a miniaturization may be possible, while the cost thereof may be able to be reduced. However, since the photosensitive medium is needed to be rotated four times to form a color image on a single sheet of a recording medium, the printing speed is low, thereby difficult to perform a color registration.
Thus, as to enhance the printing speed of the image forming apparatus of a multi pass scheme, in a stage that the exposure, the developing, and the intermediate transfer with respect to the last color are performed, a transfer roller needs to contact with an intermediate transfer belt, so that the transfer to a recording medium may take place. At this time, by the impact generated as the transfer roller and the intermediate transfer belt are made to be in contact, a shaking may occur on the position of an exposure, and a band may occur on the toner image of the last color.
In addition, in a case when a plurality of recording media is consecutively being printed, as to shorten the printing time, in the stage in which the exposure, the developing, and the intermediate transfer take place with respect to the first color of the next recording medium, a cleaning task is being performed to remove the remaining toner. The cleaning task applies a load to the intermediate transfer belt and causes a speed change, thereby generating the registration offset of the first color.